The green credentials the nuclear power industry claims rest on two factors: uranium is effectively inexhaustible and power stations' carbon dioxide emissions are very low.

On uranium, Gordon MacKerron, an energy expert at the University of Sussex, says: "We are extremely unlikely to run short of uranium for a very long time." The suggestion that good quality uranium supplies are becoming scarce is fanciful, he adds. Much of the planet's uranium supplies are yet to be surveyed and with new markets emerging in Namibia and Kazakhstan the supply of nuclear fuel is not expected to peak until 2015 at the earliest.

Precisely how long this can be made to last remains unclear. "Some say we have enough to last for 60 years, and others put it at 360 years," says Adisa Azapagic, who is heading a sustainability assessment of nuclear power at the University of Manchester. Such uncertainty depends partly on the amount of growth of nuclear power in the coming decades, but also on the kinds of nuclear technology employed – improvements in reactors make it possible to squeeze far more out of each lump of fuel. In fact, according to MacKerron, over the last few decades the burn-up rate has increased so much that a lump of uranium will last up to three times longer than in the 1970s.

In terms of emissions, nuclear power is often described as having no CO2 emissions; this is only really true once a nuclear plant is operational, says Azapagic. The mining and preparation of the fuel and the construction of the power plants all carry a carbon price tag.

However even when this is taken into account, nuclear comes out looking relatively clean. Plants produce on average 2-20 tonnes of carbon per gigawatt-hour of energy. According to a report by the Sustainable Development Commission, the government's independent watchdog, this makes nuclear power orders of magnitude better than fossil fuels and on a par with wind power.